Siren



Nov. 19, 1940. K. A. SCHMACKE 2,222,322

' SIREN Filed Feb. 3; 1958 2 Sheets-Sheet l Du/272 i0 2".-

Ncxv. 19, 1940. K. A. SCHMACKE 2,222,322

- v SIREN Fil'ed Feb. 3 1938 Sheets-Shet 2 Patented Nov. 19, 1940 UNITED STATES PATENT OFFICE SIREN Karl August Schmacke, Hagen, Westphalia, Germany 2 Claims.

This invention relates to improvements in sirens, more particularly in those intended to be used as an alarm device in the case of air raid danger. Such sirens must be capable of emitv ting a high as well as a deep or low continuous sound. With the usual method of driving sirens by means of an electric motor, the shaft of which is fitted with fixed blades, the high continuous note is emitted for instance at 3000 revolutions per minute, and the low continuous tone at 1500 R. P. M. Since, however, decreasing speed causes lowering of the pitch, and high pitch notes have a greater distance of audibility than low pitch notes, it is obvious that the range of the deep continuous note decreases with the decreasing speed, which is undesirable.

Experiments have shown that the range at which the high continuous note is heard, is the greatest when it has perceptible overtones or harmonics in its frequency spectrum. Such harmonies are, however, a drawback for the deep continuous sound, the purity of which is greatly affected by the harmonics so that it becomes difficult to differentiate it from the high note.

Sirens with several bladed Wheels for high and deep continuous notes driven by one and the same motor, are already known. These sirens have, however, the drawback that all the wheels are simultaneously driven by the motor as they'are rigidly secured to its shaft. All the tones are therefore produced simultaneously. A mixed note of high and low tones is therefore produced.

In the case of sirens which are to be used for air raid danger, it is necessary, however, to pro- 35 duce a high or a low tone in order to indicate whether the danger still exists or has passed.

Two individual separate sirens, each with a bladed wheel, one siren having a high pitch and the other a low pitch, have been generally used, 40 each siren being started individually and independently of the other.

It is therefore known to use sirens with several bladed wheels driven by one and the same motor, for producing mixed tones, and sirens with only one bladed wheel driven by the motorshaft, which is intended to produce either a high or a low note, but not mixed notes.

In order to obtain the advantage of being able to use a single drive for several bladed wheels, and a simplified construction for erecting such sirens, two bladed wheels of one siren are mounted loosely on the motor shaft to which they can be alternately coupled at will to obtain a high or a low continuous note.

As already explained, even one siren could be arranged for instance on the shaft of an electric motor and caused to produce a high or a low note by altering the speed of the motor shaft, but in the case of the low note, the speed must be substantially reduced, whereby the distance at 5 which the low continuous note is heard is also reduced.

The invention consists in using as the means for coupling two bladed wheels to a driving shaft, 7 which is preferably the shaft of an electric motor, 16 free-wheeling clutches of the well known kind, but operative in opposite directions, owing to which, with changing direction of rotation of the motor shaft, either one or the other bladed wheel is caused to take part in the rotation of the driv- 5 ing shaft (electric motor shaft) whilst the other one is stopped.

As however with this arrangement there is also the danger that the uncoupled bladed wheel will still continue to rotate, even though at a smaller 20 speed, and produce disturbing undertones, according to the invention there is also provided at the same time a free-wheeling clutch, though a smaller one, for coupling the bladed wheel rotating in the reverse direction, to a fixed part of 5 the housing, owing to which one bladed wheel is locked at once when the other one is positively driven from the motor shaft.

The invention makes it further possible to arrange the two siren blades at both ends of the 3 motor or of the motor shaft, and as separate room is no longer required for a coupling, substantially to reduce the constructional length of double sirens. The drawings show by way of example one form of a double siren driven by an electric motor.

In said drawings:

Fig. 1 is a sectional view of a double siren;

Fig. 2 is an enlarged View of part of Fig. 1;

Fig. 3 is a section on the line IIIIII of Fig. 2;

Fig. 4 is a section on the line IVIV of Fig, 2;

Fig. 5 is :an external view of the complete apparatus.

In the support l of the siren, preferably built as a hollow cylinder, is rigidly mounted an electric reversing motor 2. On the motor shaft 1 are loosely mounted two bladed wheels 8. The upper wheel comprises for instance eight blade segments 3 which are at right angles to a common circular bottom plate or disc Ill, and are held together at the other end by a. tension ring 4.

The siren casing 5 is either made in one piece with the casing I, or put on the support separately. The cylindrical part of the siren casing 5 is provided, opposite the blade segments 3, with apertures 6, the number of which may be any desired. The arrangement of the sirens in themselves, that is to say of the siren blade and of the corresponding casing, is in accordance'with the well known siren constructions.

Exactly the same siren as that shown in Figs. 1 and 2 above the electric motor, is mounted also at the other free end of the motor shaft below the motor, so that a double siren is produced. The motor shaft 1 is of similar construction at both ends, which are each provided with rotors of similar form. One of the sirens, in the present case the upper one, is arranged to emit a high continuous note, and the other siren a low continuous note.

The arrangement of the sirens under and above the electric motor 2 is preferably such that the discs IB face each other.

Referring to the upper part of Fig. 1, the motor shaft is supported by a ball bearing II in the motor housing. The bearing pin or spindle 9 of the motor shaft is supported relatively to the vane wheel by a further ball bearing l2. To the spindle 9 is secured an annular collar l3 of bronze or the like, opposite which is a bushing M, also of bronze, of the vane wheel 8. Between the bodies !3 and 8 are arranged the rollers I5 and 28 of a free-wheeling clutch (Figs. 2 and 3). To the vane wheel 8 is further connected a screwed-on cap l5 secured to a hollow sleeve I I. On the latter is mounted a fixed bronze ring i8, opposite which is an also fixed bronze ring IS in the cover 20 of the casing.

Between the bodies l8 and I9 are arranged rollers 2! of a smaller free-wheeling clutch (Figs. 2 and 4). With the shaft F rotates only the sleeve 13. When the motor shaft is rotated for instance in the clockwise direction, the free-wheeling clutch at [5 becomes operative and effects the connection to the vane wheel 8.

When the vane wheel 8 is rotating jointly with the shaft 1, the sleeve ll, and with it the bronze ring It also take part in the rotation. On the contrary, the rollers 2! which respond to a rotation in the anti-clockwise direction, remain inoperative. In the siren at the lower end of the motor shaft, the free-wheeling clutches are arranged exactly in the reverse way. Otherwise the arrangement is exactly the same. On the shaft 1 being rotated in the anti-clockwise direction, the bladed wheel of the lower siren Will be driven,

whilst the free-wheeling clutch of the bladed wheel 8 of the upper siren will become disengaged and will no longer be driven. If, however, the latter tends to take part in a rotation corresponding to that of the lower bladed wheel, that is to say in the anti-clockwise direction, either owing to the shaft friction or to the draught or to any other circumstances, the free-wheeling clutch of the rollers l5 and 28 will remain inoperative, but the other small free-wheeling clutch 2| will come into action. As however the cover 20 of the easing is fixed, the only consequence would be that the upper bladed wheel 8 will be unable to take part in the rotation of the motor shaft. Conversely of course the same thing will happen. As seen from Fig. 5 the air is drawn in by means of the rotors 3 through the base and cover of the apparatus and forced out through the apertures 6, thus producing the usual siren note.

For the purpose of lubrication, the sleeve I1 is bored through and connected to an oil pipe 22 through which the lubricant can be supplied from a cup 23. The lubricant gets into the chamber 24 of the cap l6 whence, as shown in the drawings, it can get into the ball bearing l2. Under the vane wheel 8 is provided a lubricant catch plate 25 with a packing ring 26. Through the motor casing is also laid a lubricant pipe 2i which leads to the ball bearing II of the shaft 1.

I claim:

1. A siren comprising two bladed wheels, one producing a high continuous note and the other producing a low continuous note, said wheels being driven by a reversing motor and mounted loosely on the same driving shaft of said motor, to which shaft the wheels may be selectively connected through one of two free wheeling clutches, one of said clutches being adapted to engage with one wheel and the other clutch being adapted to engage with the other wheel, said clutches being operative for opposite directions of rotation of the motor shaft.

2. A siren according to claim 1 comprising for each bladed wheel a second smaller reverse free wheeling clutch adapted to engage with said bladed wheel and operative in the direction opposite to the larger free wheeling clutch adapted to engage with the same wheel, the said reverse free wheeling clutch co-operating with a fixed part of the siren casing.

KARL AUGUST SCHMACKE. 

